Pressure induced hypertrophy in the hearts of growing dwarf pigs

The left ventricles of 8 sibling dwarf pigs were stressed by banding the aorta ascendens for 7 to 49 days. There was no developmental retardation. Neither light nor electron microscopic controls showed signs of insufficiency. 3.7 X 10(7) Bq/kg (1 mCi/kg) body weight (3 H-)methyl thymidine had been applied as pulse at the end of the experiment. The 3 H-index (LI) of the left ventricular wall increases with the pressure registered (r = 0.95). At the same time the values for the right ventricular wall and the left atrium showed an inverse tendency corresponding to the fact that all indices decrease during normal growth. The relation of the indices is two to one for each atrium and its corresponding ventricle, as well as for the stressed left ventricular wall to the right one. The 3 H marked cells are found in groups with constant distances (75-85 microns). High LI are the consequences of the enlargement of these groups. There is no detectable relation to an anatomic structure. Some rare mitoses could be seen, especially in the left ventricular wall. Signs of a high biochemical activity are accumulations of mitochondria, high number of polysomes and large Golgi areas as well as laminas of ergastoplasm. The nuclei are extremely invaginated.